Examples of a cuffing tool (cutting insert) include a cubic boron nitride cutting tool formed by, for example, joining a small piece of a sintered cubic boron nitride compact to a corner portion of a polygonal base metal, made of a material such as cemented carbide, ceramics, cermet, or sintered alloy, and forming a cutting edge at the sintered cubic boron nitride compact.
The cubic boron nitride cutting tool that does not include a breaker protrusion or a breaker groove is finished in such a manner that the top face of the base metal and the rake face formed on the sintered cubic boron nitride compact are flush with each other. Cuttings using a cubic boron nitride tool include various applications, each requires appropriate edge processing. In the case where the sharpness is required, cutting is performed using a tool having a sharp edge or a tool having a honed edge. In the case where the strength is required, cutting, is frequently performed using a tool including a sintered cubic boron nitride compact, which is hard and fragile, on which a cutting edge is formed while a negative rake face is formed at the cuffing edge to strengthen the cutting edge.
Usually, to form a rake face by grinding, a large number of cutting, tools are attached to a flat grinder and ground by a single grindstone. In this method, the base metal and the sintered cubic boron nitride compact disposed at a corner portion of the base metal are ground together (simultaneously ground) and thus, the top face of the base metal and the rake face of the sintered cubic boron nitride compact become flush with each other. Another conceivable method is to simultaneously grind the base metal and the sintered cubic boron nitride compact together to form only the flank face by finishing only the base metal or the rake face by grinding and then soldering a cubic boron nitride blank thereto.
A cubic boron nitride cutting tool in which the top face of the base metal and the rake face of the sintered cubic boron nitride compact are flush with each other is disclosed by, for example, Patent Literature (PTL) 1. Such cubic boron nitride cutting tools are also described in catalogues disclosed through the Internet by various tool manufacturers (for example, Sumitomo Electric Hardmetal Corporation, Tungaloy Corporation, Mitsubishi Materials Corporation, or Sandvik AB).